Design and fabrication of a four-channel CWDM cooled DFB-LD module with OSFP electrical interface for CPO external laser sources

To mitigate severe thermal challenges within co-packaged optics (CPO) modules and prevent adverse effects on electrical or silicon photonic chip performance, the optical transmitter can effectively utilize an external laser source (ELS). This article presents the design, fabrication, and testing methodology of a four-channel coarse wavelength division multiplexing (CWDM) cooled distributed feedback laser diode (DFB-LD) module explicitly developed for CPO ELS applications. We selected AlGaInAs multiple quantum well (MQW) DFB-LDs with nominal wavelengths of 1265 nm, 1285 nm, 1305 nm, and 1325 nm to meet the requirements of O-band CWDM systems. Thermoelectric coolers (TECs) and thermistors are integrated into the module to achieve precise temperature control and stable monitoring of the DFB-LDs’ operating temperature, which is crucial for maintaining laser performance. To optimize fiber coupling efficiency, lenses are placed at the LD output facet, and optical isolators are incorporated to prevent back-reflections from the fiber from negatively impacting the DFB-LD chips. The electrical interface of this module complies with the Octal Small Form-factor Pluggable (OSFP) specification, a design choice aimed at facilitating commercialization and simplifying system integration. At a 200 mA bias current, the coupled output power of each channel through a standard single-mode fiber (SMF) exceeds 30 mW, with a coupling efficiency of approximately 50%, demonstrating the module’s potential as an external light source in CPO systems. This paper elaborates on the key steps from design considerations to practical manufacturing, assembly, and performance verification, aiming to provide valuable practical guidance for engineers and researchers in related fields.